package app

import (
	"encoding/json"
	"fmt"

	"gitea.maximumdirect.net/eric/weatherreporter/internal/briefing"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/collect"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/config"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/generatedtext"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/module"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/promptinput"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/weatherdata"
)

// preparedReport contains the immutable deterministic inputs shared by prompt
// executions for one resolved report.
type preparedReport struct {
	resolved         report.Resolved
	reportFacts      ReportFacts
	moduleSnapshot   module.Snapshot
	briefingMetadata briefing.Metadata
	sourceWarnings   []weatherdata.SourceWarning
	dataPackage      []byte
	handler          generatedtext.Handler
}

type prepareReportRequest struct {
	Config     config.Config
	Resolved   report.Resolved
	Collection collect.Result
}

type preparationError struct {
	operation string
	err       error
}

func (e *preparationError) Error() string {
	return e.operation + ": " + e.err.Error()
}

func (e *preparationError) Unwrap() error {
	return e.err
}

func prepareReport(req prepareReportRequest) (preparedReport, error) {
	if req.Collection.Bundle == nil {
		return preparedReport{}, &preparationError{operation: "prepare report", err: fmt.Errorf("collected weather bundle is required")}
	}

	reportFacts, err := BuildReportFacts(ModuleSnapshotRequest{Config: req.Config, Resolved: req.Resolved}, req.Collection.Bundle)
	if err != nil {
		return preparedReport{}, &preparationError{operation: "build report facts", err: err}
	}
	moduleSnapshot, err := BuildModuleSnapshotFromFacts(ModuleSnapshotRequest{Config: req.Config, Resolved: req.Resolved}, reportFacts)
	if err != nil {
		return preparedReport{}, &preparationError{operation: "build module snapshot", err: err}
	}
	metadata := briefing.BuildMetadata(briefingBuildContext(req.Config, req.Resolved, reportFacts.Collected))
	dataPackage, err := promptinput.Build(promptinput.BuildRequest{Metadata: promptMetadata(metadata), Modules: moduleSnapshot})
	if err != nil {
		return preparedReport{}, &preparationError{operation: "build data package", err: err}
	}
	serializedDataPackage, err := promptinput.MarshalYAML(dataPackage)
	if err != nil {
		return preparedReport{}, &preparationError{operation: "marshal data package", err: err}
	}
	handler, err := generatedtext.LookupDefinition(req.Resolved.Definition)
	if err != nil {
		return preparedReport{}, &preparationError{operation: "lookup generated text catalog", err: err}
	}

	clonedFacts, err := clonePreparedValue(reportFacts)
	if err != nil {
		return preparedReport{}, &preparationError{operation: "copy prepared report facts", err: err}
	}
	clonedSnapshot, err := clonePreparedValue(moduleSnapshot)
	if err != nil {
		return preparedReport{}, &preparationError{operation: "copy prepared module snapshot", err: err}
	}
	clonedMetadata, err := clonePreparedValue(metadata)
	if err != nil {
		return preparedReport{}, &preparationError{operation: "copy prepared briefing metadata", err: err}
	}
	prepared := preparedReport{
		resolved:         cloneResolved(req.Resolved),
		reportFacts:      clonedFacts,
		moduleSnapshot:   clonedSnapshot,
		briefingMetadata: clonedMetadata,
		sourceWarnings:   append([]weatherdata.SourceWarning(nil), clonedMetadata.SourceWarnings...),
		dataPackage:      append([]byte(nil), serializedDataPackage...),
		handler:          handler,
	}
	return prepared, nil
}

func cloneResolved(value report.Resolved) report.Resolved {
	cloned := value
	cloned.Definition.DistributorPathTemplates = append([]string(nil), value.Definition.DistributorPathTemplates...)
	cloned.Definition.Modules = make([]module.ConfigItem, len(value.Definition.Modules))
	for i, item := range value.Definition.Modules {
		cloned.Definition.Modules[i] = item
		switch options := item.Options.(type) {
		case module.AreaForecastDiscussionOptions:
			options.Sections = append([]string(nil), options.Sections...)
			cloned.Definition.Modules[i].Options = options
		}
	}
	return cloned
}

func (p preparedReport) dataPackageCopy() []byte {
	return append([]byte(nil), p.dataPackage...)
}

func (p preparedReport) sourceWarningsCopy() []weatherdata.SourceWarning {
	return append([]weatherdata.SourceWarning(nil), p.sourceWarnings...)
}

func (p preparedReport) renderInputs() (briefing.Metadata, module.Snapshot, ReportFacts, error) {
	metadata, err := clonePreparedValue(p.briefingMetadata)
	if err != nil {
		return briefing.Metadata{}, module.Snapshot{}, ReportFacts{}, err
	}
	snapshot, err := clonePreparedValue(p.moduleSnapshot)
	if err != nil {
		return briefing.Metadata{}, module.Snapshot{}, ReportFacts{}, err
	}
	reportFacts, err := clonePreparedValue(p.reportFacts)
	if err != nil {
		return briefing.Metadata{}, module.Snapshot{}, ReportFacts{}, err
	}
	return metadata, snapshot, reportFacts, nil
}

func clonePreparedValue[T any](value T) (T, error) {
	encoded, err := json.Marshal(value)
	if err != nil {
		var zero T
		return zero, fmt.Errorf("marshal immutable prepared value: %w", err)
	}
	var cloned T
	if err := json.Unmarshal(encoded, &cloned); err != nil {
		var zero T
		return zero, fmt.Errorf("unmarshal immutable prepared value: %w", err)
	}
	return cloned, nil
}